Showing papers by "University of Buenos Aires published in 1980"

Enhancement of hydrogen peroxide formation by protophores and ionophores in antimycin-supplemented mitochondria

Abstract: Rat and pigeon heart mitochondria supplemented with antimycin produce 0.3-1.0nmol of H(2)O(2)/min per mg of protein. These rates are stimulated up to 13-fold by addition of protophores (carbonyl cyanide p-trifluoromethoxyphenylhydrazone, carbonyl cyanide m-chloromethoxyphenylhydrazone and pentachlorophenol). Ionophores, such as valinomycin and gramicidin, and Ca(2+) also markedly stimulated H(2)O(2) production by rat heart mitochondria. The enhancement of H(2)O(2) generation in antimycin-supplemented mitochondria and the increased O(2) uptake of the State 4-to-State 3 transition showed similar protophore, ionophore and Ca(2+) concentration dependencies. Thenoyltrifluoroacetone and N-bromosuccinimide, which inhibit succinate-ubiquinone reductase activity, also decreased mitochondrial H(2)O(2) production. Addition of cyanide to antimycin-supplemented beef heart submitochondrial particles inhibited the generation of O(2) (-), the precursor of mitochondrial H(2)O(2). This effect was parallel to the increase in cytochrome c reduction and it is interpreted as indicating the necessity of cytochrome c(1) (3+) to oxidize ubiquinol to ubisemiquinone, whose autoxidation yields O(2) (-). The effect of protophores, ionophores and Ca(2+) is analysed in relation to the propositions of a cyclic mechanism for the interaction of ubiquinone with succinate dehydrogenase and cytochromes b and c(1) [Wikstrom & Berden (1972) Biochim. Biophys. Acta283, 403-420; Mitchell (1976) J. Theor. Biol.62, 337-367]. A collapse in membrane potential, increasing the rate of ubisemiquinone formation and O(2) (-) production, is proposed as the molecular mechanism for the enhancement of H(2)O(2) formation rates observed on addition of protophores, ionophores and Ca(2+).

Mechanism of immune transfer by RNA extracts. Immune RNA induces the synthesis of idiotype-bearing antigen receptors in noncommitted cells.

Abstract: Immune RNA (I-RNA) was extracted from lymphoid organs of BALB/c mice immunized with AKR lymphoid cells. Incubation of normal BALB/c spleen cells with this I-RNA (but not with normal RNA) resulted in leukocyte migration inhibition reactions (LMIR) against AKR extracts but not against purified protein derivative or BALB/c sarcoma extracts. This transfer was abolished by pretreating I-RNA with RNAse but not with pronase. The active fraction of I-RNA was retained by and could be eluted from Poly-U Sepharose columns. Normal cells pretreated with I-RNA also reacted in the presence of an anti-idiotypic anti-serum of anti-(BALB/c anti-AKR) specificity. Pretreatment of cells with anti-idiotypic serum plus complement did not inhibit the subsequent transfer of LMIR with I-RNA. Idiotypic receptors were expressed on I-RNA treated cells less than one hour after I-RNA treatment. Using an I-RNA of double specificity, the results suggested that I-RNA entered into and acted on the cells through a nonspecific mechanism. Finally, I-RNA could induce BALB/c anti-AKR idiotypic markers in C57B1/6 cells, genetically committed for different idiotypes, while RNA extracted from C57131/6 immune cells could not induce in BALB/ c cells their own genetically acquired idiotypes. This series of data would prove that I-RNA acting as a mRNA is able to induce in normal noncommitted cells the de novo synthesis of antigen receptors similar or identical to those present in the surface of in vivo immunized lymphoid cells of the same strain.

Chronic self-stimulation of the medial posterior inferior thalamus for the alleviation of deafferentation pain.

Abstract: Since current techniques yield uncertain results on deafferentation pain, chronic brain Stimulation may presumably be a valuable alternative method, without deterrent side-effects. Disappointing results with stimulation of the somato-sensory structures prompted the selection of the medial posterior inferior thalamus and adjascent brain stem for chronic stimulation in pain states of central origin. Six such cases are reported. Abolition of the hyperpathia and marked reduction in the deep background pain was achieved in 2 cases, and disappearance of the hyperpathia and moderate reduction in the deep pain was obtained in another 2, but none had complete alleviation of pain. The follow-up time ranged between 6 and 42 months. Reversal of analgesia by naloxone was not observed. Acute experimentally-induced pain was not modified by Stimulation.

The Activity of Ketoconazole in the Treatment of Onychomycosis

Abstract: Ketoconazole was administered orally in daily doses of 200 mg to 70 patients with onychomycosis. Complete recovery was attained by 48 patients, improvement of > 50% by 10 patients, and for three patients therapy failed. For the remaining nine patients the results could not be evaluated. The average duration of treatment was 7.5 months for disease due to Trichophyton species and 6.5 months for disease due to Candida species. There were no adverse effects or signs of toxicity attributable to the administration of ketoconazole. It is concluded that ketoconazole is a positive development in the effort to control the difficult problems presented by onychomycosis.

Chronic self-stimulation of the dentate nucleus for the relief of spasticity.

Abstract: It has been assumed but not yet proved that cerebellar cortical Stimulation activates the Purkinje cells, with subsequent inhibition of the deep cerebellar nuclei. However, the relatively crude, widespread excitation induced by several surface electrode arrays and the parameters of Stimulation currently used, may produce other effects than selective activation of only one specific cellular type which, furthermore, seems to be rarely present in these particular patients, as demonstrated by biopsy studies prior to electrode placement.

Palaeomagnetism of Upper Precambrian rocks of the La Tinta Formation, Argentina

Abstract: Summary Palaeomagnetic data from 77 hand samples collected in sequences of marine sediments of Late Precambrian age (709 ± 24 Myr) exposed at two zones (Olavarria—Sierras Bayas and Barker) in central Argentina (37.3° S 59.8° W, La Tinta Formation) are given. After thermal cleaning and chemical leaching, the samples show normal and reversed polarity and yield a palaeomagnetic pole at 300.9° E 79.3° S (α95=4.8°). The position of this pole supports the interpretation that Gondwana was a unit in Late Precambrian times and is consistent with the Late Precambrian glaciation (Marinoan) of south-eastern Australia. The direction and polarity of the stable RM of samples and the change of direction of the stable RM for adjacent samples along a sequence are used to correlate La Tinta rocks within a zone and between the two zones.

Brain catecholamines modifications. The effects on memory facilitation induced by oxotremorine in mice.

Abstract: The immediate posttrial injection of oxotremorine (0.250 μMol/kg, IP) can facilitate the retention of a passive-avoidance response in mice. After the administration of alfa-methyl-p-tyrosine methylester (α-MPT) by intracerebroventricular injection at doses that had no effect on retention (100 μg, 10 μl, 60 min before trial), the immediate posttrial injection of oxotremorine did not enhance retention.

Biochemistry of thyroid regulation under normal and abnormal conditions

Abstract: Perhaps in an oversimplified view, abnormal thyroid growth can be classified into two main categories: a) those cases due to excess of thyroid stimulators extrinsic to the gland; b) situations in which an intrinsic alteration in the gland occurs: Extrinsic (excess thyroid stimulation) Iodide deficiency with elevated TSH Goitrogens Graves' immunoglobulins Thyroid stimulating factors produced by tumors Dishormonogenesis with hypothyroidism Intrinsic (normal TSH) Increased sensitivity to TSH (iodine depletion) Altered autoregulation (?) Abnormal TSH receptor Other biochemical abnormalities From the studies performed in animals it can be concluded that since goiter appears before a detectable increase in serum TSH occurs, an intrinsic alteration in the thyroid gland would be responsible for the onset of growth. Under these conditions TSH would play a permissive role in promoting and maintaining the gland enlargement. In some aspects this situation is similar to that of certain endemic goiter areas. It may be postulated that under a mild iodine deficiency a decrease in thyroidal iodine concentration occurs (and/or in certain iodocompounds), thus rendering the gland more sensitive to the stimulatory action of TSH, and leading to the appearance of goiter. If this mechanism is able to maintain an euthyroid status no further alterations will occur. In more severely iodine deficient areas, or when additional factors such as dietary goitrogens are present, hypothyroidism develops and TSH is clearly elevated. A similar localized mechanism can be postulated for the development of nodular goiter. It is more difficult to explain the pathogenesis of goiter and tumors in nonendemic areas, since the biochemical findings so far reported are not conclusive. It seems likely that an alteration of the TSH receptor is a common factor to many tumors in man and animals. However, some contradictory results would preclude us from making a general statement. The wide variety of biochemical alterations reported would perhaps indicate, that there is not a single cause for the rise of abnormal thyroid growth and that different factors may play a role in the regulation of growth under such circumstances. It is to be hoped that future studies will provide a better comprehension of this problem.

Carpal ankylosis in juvenile rheumatoid arthritis

Abstract: Forty-seven of 100 consecutive juvenile rheumatoid arthritis patients with wrist arthritis were found to have ankylosis at the carpal joints. this finding was significantly more frequent in juvenile than in adult rheumatoid arthritis patients. The carpometacarpal wrist segment was the most frequently ankylosed. Ankylosis was not related to any particular feature of the disease, but disease duration was longer in patients with ankylosis. A significant association was found between carpal ankylosis and cervical apophyseal joint fusion.

Adenosine triphosphatase from Trypanosoma cruzi: purification and properties

Abstract: 1. 1. The procedure here described for the purification of coupling factor F1 from Trypanosoma cruzi includes: (a) epimastigote fractionation; (b) chloroform extraction of the kinetoplast-mitochondrial fraction; (c) chromatography on DEAE-cellulose; (d) gel-filtration on Sephadex G-200. The yield based on the kinetoplast mitochondrial fraction was about 18% and the purification achieved was 55-fold. 2. 2. Native F1 was homogeneous, as assayed by gel-filtration on Sephadex G-200 and polyacrylamide gel-electrophoresis (mol. wt 347,000 daltons). Polyacrylamide gel-electrophoresis of depolymerized F1 showed four subunits (α, β, γ and δ). 3. 3. Fluoresceinmercuriacetate (0.7μM), p-chloromercuribenzoate (2.5 μM) and N-ethylmaleimide (0.48 mM) were effective inhibitors of F1 (in parentheses the I50 inhibitory concentration). The inhibition by the mercurials was completely reversed by 2-mercaptoethanol. 4. 4. Kinetic analysis of F1 demonstrated a biphasic linear Lineweaver Burk relationship (Km = 0.066 and 0.19 mM), thus revealing the existence of high and low affinity kinetic systems. Efrapeptin inhibited both systems in accordance with a mixed type of inhibition. Rates of hydrolysis of nucleoside triphosphates decreased in the order ATP > GTP > ITP ⪢ UTP = TTP = CTP. Nucleoside diphosphates were not hydrolysed but ADP inhibited activity. 5. 5. F1 was cold-labile but could be kept for at least 20 days at −70°C when dissolved in 50% (v/v) glycerol/50 mM Tris∗-1.0 mM EDTA 2 mM ATP buffer (pH 7.6). The half-life of F1 in the Tris-EDTA-ATP solution at 4°C was increased four to five times by the addition of 10% (v/v) ethanol or by the replacement of H2O by D2O.

Blood sugar, serum insulin and serum free fatty acid responses to slow graded glucose in thyroxine-treated dogs

Abstract: The effects of short-term (10 days) thyroxine administration (100 µg/kg body weight/die) on the BS, serum IRI and circulating FFA responses to slow, graded glucose stimulation were studied in dogs. The experiments reported demonstrated that the mean basal BS value in thyroxine-treated dogs is higher than that found in untreated controls, and that non-parallel mean BS responses to glucose infusion were observed during the test: the higher curve was found in the thyroxine-treated group. Mean basal serum IRI was similar in both groups, and parallel insulinemic responses to hyperglycemia were observed. Mean serum IRI responses as a function of time from the start of infusion in hyperthyroid dogs were lower than those observed in untreated controls. Mean basal serum FFA levels in both groups did not differ, and parallel serum FFA curves were found during the test. Thyroxine treatment caused a better lipogenic response to combined hyperglycemia/hyperinsulinemia and a steep subsequent rebound of serum FFA, as compared to untreated controls. We conclude that dogs with recently induced hyperthyroidism show an impairment in the net glucose uptake by tissues, a poor insulinemic response to glucose, a good lipogenic response and a sharp subsequent rebound of serum FFA. The high BS curve, the high tissue FFA response to insulin antagonists and the high mean BS level in the fasting condition might be accounted for by a thyroxine-induced active production of cAMP in body cells, but the low insulin secretion evidently is due to other mechanisms.

Convolution and correlation using delta modulators

Abstract: The simplicity of addition and multiplication using delta modulated signals is achieved in a system used to implement a correlator and a convolver. If one signal is a pseudonoise (PN), the system can be simplified further.

Double-blind controlled trial of molsidomine in hypertension

Abstract: Molsidomine (M), a new long-lasting antianginal compound, was studied in 38 hypertensive patients to assess its antihypertensive properties. Six patients were selected for an acute, single dose comparative trial with placebo over 8 h after treatment. The remaining 32 patients were used in a 1 month trial to study the effect on BP of more prolonged treatment. Systolic, diastolic and mean BP were significantly reduced after a single dose of M 4 mg, and the effect lasted for about 8 h. M also inhibited the hypertensive response to isometric exercise in handgrip tests performed 1 and 8 h after M ingestion. A dose-related decrease in systolic and diastolic BP in the one month trial was also observed. In addition to its antianginal properties, M appears to possess an interesting effect on BP in mildly to moderately hypertensive patients. A fall in BP is also a valuable effect in coronary patients with augmented metabolic demands of the heart.